It is already understood in automotive engineering that a synchronous machine excited by a permanent magnet (PM synchronous machine) may be installed in the drive train of a vehicle as an integrated crankshaft starter generator between the internal combustion engine and the transmission.
Such a PM synchronous machine is regulated in the rotor-field-oriented coordinate system. FIG. 1 shows an example of field-oriented current regulation of a PM synchronous machine having a pulse-width-modulation inverter. This is based on an actual value measurement of the phase currents of a three-phase system and determination of a direct-axis component and a quadrature-axis component of the regulating voltage with respect to the rotor position, based on actual measured values. The quadrature-axis component of current is proportional to the desired torque.
With this regulation, phase currents ia, ib, ic derived from the three-phase system of the PM machine are converted in a Park transformer 13 into Id_actual and Iq_actual currents of a rectangular coordinate system. Current Id_actual is the actual value for the direct-axis component of current of the machine. Current Iq_actual denotes the actual value for the quadrature-axis component of current of the machine.
Actual value Id_actual of the direct-axis current component is sent via a heterodyne element 12 to a direct-axis current component regulator 1, and actual value Iq_actual of the quadrature-axis current component is sent as the actual value to a quadrature-axis current component regulator 2. Heterodyne element 12 receives as another input signal a feedback signal which is obtained from output quantity uq′ of a stationary decoupling network 5. In addition to achieving the decoupling which is important for the regulating effect, stationary decoupling network 5 also fulfills the function of achieving field weakening on direct-axis current component regulator 1 in the upper rotational speed range in conjunction with output limiters 3 and 4 and an anti-windup method. This field weakening of the PM synchronous machine at higher rotational speeds is necessary because otherwise the induced machine voltage would be greater than the maximum power converter output voltage. The latter is limited by the power supply voltage, i.e., the vehicle electrical system voltage. In this field weakening operation, the power converter is operated in an override state, so the power converter output voltage is no longer sinusoidal.
The setpoint input of direct-axis current component regulator 1 receives a setpoint signal generated by a direct-axis current component setpoint generator 9 and the setpoint input of quadrature-axis current component regulator 2 receives a setpoint signal generated by a quadrature-axis current component setpoint generator 14. Quadrature-axis current component setpoint generator 14 generates the quadrature-axis current component setpoint signal as a function of the output signal of a battery voltage sensor.
At the output of direct-axis current component regulator 1, a manipulated variable Id* for the direct-axis current component is made available, and at the output of the quadrature-axis current component regulator 2 a manipulated variable Iq* is made available for the quadrature-axis current component. These manipulated variables are sent to stationary decoupling network 5 which determines a direct-axis voltage component ud′ and a quadrature-axis voltage component uq′ for the regulating voltage of the PM synchronous machine using the manipulated variables mentioned above.
These regulated voltage components ud′ and uq′ which are regulated voltage components in the rectangular coordinate system, are sent via output limiters 3 or 4 to an inverse Park transformer 6, which has the function of converting regulated voltage components ud and uq which are limited in the rectangular coordinate system to regulated voltage components ua, ub and uc of the three-phase system. These are converted in a pulse inverter 7 into triggering pulses for PM synchronous machine 8.
Quadrature-axis voltage component uq′ of the regulated voltage output at the output of stationary decoupling network 5 is sent to absolute value generator 10, which determines absolute value |uq′| of the quadrature-axis voltage component.
The output signal of absolute value generator 10 is used as the input signal for a threshold value switch 11. If absolute value |uq′| exceeds a predetermined threshold value, then the value 0 is output at the output of threshold value switch 11. If absolute value |uq′| falls below the predetermined threshold value, then the value 1 is output at the output of threshold value switch 11.
Exemplary embodiments of a decoupling network in which a stationary machine model is stored are discussed and described in German patent document no. 100 44 181.5 by the present applicant
German patent document no. 100 23 908 discusses a method for determining the rotor position of an electric machine which may be, for example, a three-phase generator having a pulse-width-modulation inverter, with a rotor winding, a stator equipped with inductors and a voltage source situated between two phase terminals also being provided. In this method, using switching elements provides for branching into two phases in which the particular phase voltage characteristics are measured. Superimposing them permits an unambiguous determination of the rotor position. In the case of this method, the rotor positions for each voltage curve are stored in the form of tables.
In addition, the journal ETEP, Vol. 8, No. 3, May/June 1998, pp. 157-166 discusses a permanent-magnet synchronous machine having field-weakening operation in which there is a large ratio of maximum speed to basic speed. This is achieved by an additional negative D component of the stator current. As part of the regulation of an available synchronous machine, the rotor position is measured using the output signals of three Hall sensors, one Hall sensor being assigned to each phase U, V and W.